reached by the same genera in the upstream area. The August and September 

 population densities of Capnia and Baetinae, however, exceeded those re- 

 corded in the upstream area. 



At McManus Creek, the mined area densities of Oligochaeta and 

 Rhyacophila did not reach those recorded in the upstream area; the mined 

 area densities of Alloperia, Ch ironom i dae, and Tipulidae exceeded the up- 

 stream area densities on each of the two succeeding trips. The failure of 

 the mined area densities of some taxa to reach upstream densities, while 

 those of other species exceeded the upstream densities, indicated that there 

 was a long-term habitat alteration which has led to an alteration in species 

 composition of the mined area. Another site which showed a similar response, 

 but where an aufeis field was not identified, was the Penny River site, 

 where mined area densities of Oligochaeta, Nemoura, C i nygmu I a , Ch i ronomi dae, 

 and others were general ly lower than upstream densities. In the Penny River 

 mined area, population densities of Tipulidae and, at times Capnia, 

 Baetinae, Ephemerella, and Athericidae were higher than those in the up- 

 stream area. The shift in taxa at the above sites appeared to be related to 

 the occurrence of unstable substrate possibly aggravated by an aufeis field. 



Other sites with a similar substrate alteration (Washington Creek, 

 Kuparuk River) also showed density reductions of most organisms but the site 

 was only visited once and this precluded any analysis of recovery or sea- 

 sonal patterns. At Kuparuk River, densities of al I species were lower in the 

 mined area than in the upstream area while at the Washington Creek upper 

 mined area, only Tipulidae densities exceeded those in the upstream area. In 

 summary, certain taxa, primarily Oligochaeta, Nemoura, Cinygmula, and 

 Chironomidae were reduced in areas of unstable substrate while others, 

 primarily Tipulidae, but also Capnia and Baetinae, showed increased den- 

 sities. 



Response to Increased Braiding . Aquatic macro i nvertebr ate responses to 

 these alterations were colonization by taxa which are more suited to lower 

 velocity waters with higher organics. Clinging ephemeropt erans, as found in 

 the family Hept agen i i dae (Cinygmula, Epeorus), were replaced by sprawlers 



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